Controlling web tension, and accumulating lengths of web, by actively controlling velocity and acceleration of a festoon

Abstract

This invention pertains to processing continuous webs such as paper, film, composites, and the like, in dynamic continuous processing operations. More particularly, it relates to accumulating limited lengths of such continuous webs and to controlling tension in such continuous webs during the processing operation. Both tension control and limited accumulations are achieved in a festoon system by connecting a corresponding festoon to actuator or the like, sensing variables such as position, tension, velocity, and acceleration parameters related to the web and the festoon, and providing active force commands, in response to the sensed variables, to cause translational movement, generally including a target acceleration, in the upper festoon rolls to control tension disturbances in the web while providing limited accumulation of a length of the web. In some applications of the invention, the festoon control system is used to attenuate tension disturbances. In other applications of the invention, the festoon control system is used to create controlled tension disturbances.

Description

This invention relates to the processing of continuous webs such as paper, film, composites, or the like, in dynamic continuous processing operations. More particularly, the invention relates to controlling tension in such continuous webs during the processing operation, and to temporarily accumulating limited lengths of such continuous webs.In the paper and plastic film industries, a dancer roll is widely used as a buffer between first and second sets of driving rolls in a line of processing machines. The first and second sets of driving rolls define respective first and second nips, which drive a continuous web. The dancer roll, which is positioned between the two sets of driving rolls, is also used in detecting the difference in speed between the first and second sets of driving rolls.Typically, the basic purpose of a dancer roll is to maintain constant the tension on the continuous web which traverses the respective section of the processing line between the first and second set...

AI Technical Summary

Benefits of technology

The invention also comprehends, in a processing operation wherein a continuous web of material is advanced through a processing step defined by first and second spaced nips, each nip being defined by a pair of nip rolls, a method of controlling web tension, and of accumulating a limited length of the web, in the respective section of web. The method comprises providing a festoon, having upper and lower festoon rolls, operative on the respective section of web; applying a first generally static force component to the upper festoon rolls, the first generally static force component having a first value and direction; applying a second variable force component to the upper festoon rolls, the second...

Problems solved by technology

However, the length of web which the dancer roll can absorb is limited to that length of web which traverses the upward path to the dancer roll and the downward path from the dancer roll.

A limitation of dancer rolls, as conventionally used, is that under more dynamic circumstances, the dancer's ability to maintain constant web tension depends upon the dancer system's mass, drag, and friction.

U.S. Pat. No. 5,659,229, however, controls the velocity of the dancer ro...

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